HIP0080, HIP0081

FN3018 Rev 5.00

Page 10 of 14

November 2000

or:

Not all Integrated Circuit packages have a directly definable

case temperature because the heat is spread through the lead

frame to a PC Board which is the effective heat sink.

Calculation Example 1

For the HIP0081,

JC = 3oC/W and the worst case junction

temperature, as an application design solution, should not

exceed 150oC. For a given application, Equation 1 determines

the dissipation, PD.

Assume the package is mounted to a heat sink having a

thermal resistance of

6oC/W and, for a given application,

assume the dissipation is 3W and the ambient temperature

(TA) is 100oC. From Equation 4, JA is 9oC/W. The solution for

junction temperature (TC) by Equation 3 is:

TJ = 100oC + 3W x 9oC/W = 127oC.

Calculation Example 2:

Assume for the HIP0080,

JA = 3oC/W mounted on a PC

Board with good heat sinking characteristics. Again, the worst

case junction temperature, as an application design solution,

should not exceed 150oC. Assume from the application, based

on Equation 1, the dissipation, PD = 1.5W. The maximum

junction temperature is known and can be used to determine

the maximum allowable ambient temperature from Equation

5A as follows:

TA = 150oC - 1.5W x 30oC/W = 105oC.

Equal Current Loading Solution

Many applications may have equal current loading in the

output drivers with equal saturated turn ON and temperature

conditions. As such, a convenient method to show rating

boundaries is to substitute the dissipation Equation 2 into the

junction temperature Equation 3. For m outputs that are ON

and conducting with equal currents, where I=I1=I2.....=Im,

we have the following solution for dissipation:

The number of output drivers ON and conducting (m) may be

from 1 to n. (i.e., For all four output drivers of the HIP0081 ON,

m = 4.) Maximum temperature, dissipation and current ratings

must be observed. For a defined number of conducting Power

MOS Output Drivers, we can plot the results for m devices

showing I vs TC.

Given the HIP0081 as an example, Figures 6 and Figure 7

illustrate the boundaries for temperature and current. Figure 6

shows the maximum current for a single output ON while

Figure 7 shows the maximum current for all four outputs ON

with equal current plotted versus Case Temperature, TC.

Boundary conditions relate to the Absolute Maximum Ratings

as defined in the Data Sheet.

(EQ. 5A)

TA

TJ PD JA



–

=

(EQ. 6)

PD

mPk



mI



2

rDS ON





==

I

TJ TC

–

m



JC

rDS ON







--------------------------------------------------

=

(EQ. 7)

FIGURE 6. HIP0081 MAXIMUM SINGLE OUTPUT CURRENT vs CASE (TAB) TEMPERATURE

50

75

100

125

150

0.0

0.5

1.0

1.5

2.0

2.5

3.0

CASE (HEAT SINK TAB) TEMPERATURE (oC)

(1)

(2)

CURVE (1): rDS(ON) = 1

CURVE (2): rDS(ON) = 0.5

THERMAL RESISTANCE,

JC = 3oC/W

MAX. +IOUT(DC)